The Notch gene was first described in 1917 when a strain of the fruit fly Drosophila melanogaster was found to have notched wing blades (Morgan, Am Nat 51:513 (1917)). The gene was cloned some seventy years later and turned out to be a cell surface receptor playing a key role in the development of many different cell types and tissues (Wharton et al., Cell 43:567-581 (1985)). Since then, the gene and its molecular mechanisms have been extensively studied. The generality of the Notch pathway manifests itself at different levels. At the genetic level, many mutations exist that affect the development of a very broad spectrum of cell types in Drosophila. 
The Notch signaling pathway was soon found to be an evolutionarily conserved signaling mechanism from Drosophila to vertebrates and has been found to be involved in many cellular processes, such as differentiation, cell fate decisions, maintenance of stem cells, proliferation, and apoptosis, in various cell types during and after development (See review Artavanis, et al., Science 268:225 (1995)). Knockout mutations were found to be lethal in embryonic mice, consistent with lymphoblastic leukemia (Ellisen, et al., Cell 66(4):649-661 (1991)). The expression of mutant forms of Notch in developing Xenopus embryos interfere profoundly with normal development (Coffman, et al., Cell 73 (1993)). In humans, there have been several genetic diseases linked to Notch mutations (Artavanis-Tsakonas, et al. Science 284:770-776 (1999)).
Mammals possess four Notch proteins (designated Notch1 to 4) and five corresponding ligands (Delta-1, -3, and -4, and Jagged-1 and -2). The mammalian Notch gene encodes a ˜300 kd protein that is cleaved during its transport to the cell surface and consequently exists as a heterodimer. The extracellular portion has many epidermal growth factor (EGF)-like repeats followed by three cysteine-rich Notch/Lin12 repeats (LN) (Wharton, et al., Cell 43:567 (1985); Kidd, et al., Mol Cell Biol 6:3431 (1986); Kopczynski, et al., Genes Dev 2:1723 (1988); Yochem, et al., Nature 335:547 (1988)). The amino-terminal EGF-like repeats participate in ligand binding, whereas the Lin 12 repeats prevent signaling in the absence of ligand. The signal induced by ligand binding is transmitted to the nucleus by a process involving proteolytic cleavage of the receptor and nuclear translocation of the intracellular domain (Notch-IC). After entering the nucleus, Notch-IC competes with inhibitory proteins and recruits coactivators, including mastermind-like (MAML) proteins, and acetyltransferases. The Notch-IC complex then binds to a transcription factor RBP-J to convert it from a transcriptional repressor to an activator. The few transcriptional factors identified so far vary in their nature and effects on the cell.
Cells in pathological states often express target antigens on their surface that are present in higher concentrations than on their normal counterparts. The use of monoclonal antibodies to identify the presence of these disease markers is attractive because of their high specificities. Notch receptors have been linked to wide range of diseases, such as cancer, neurological disorders, and immune diseases, as reflected by its broad spectrum of activities in humans (Joutel, et al. Cell & Dev Biol 9:619 (1998); Nam, et al., Curr Opin Chem Biol 6:501 (2002)). Many expression studies of Notch proteins in human tissues and cell lines have been reported. For example, increased levels of Notch3 expression is found in many malignant tissues in humans. In leukemia, genetic and biochemical evidence show that Notch3 triggers multiple NF-kappaB activation pathways, which regulates distinct gene clusters involved in either cell differentitation or proliferation and leukemogenesis (Vacca, et al., EMBO J25:1000 (2006)). Notch3 is also expressed in a subset of neuroblastoma cell lines and serves as a marker for this type of tumor that has constitutional or tumor-specific mutations in the homeobox gene Phox2B, which controls part of the differentiation program of the sympathetic nervous system (van Limpt, et al., Cancer Lett 228:59 (2005)).
Notch3 is also found to be very important in the diagnosis of ovarian cancer. Advanced-stage epithelial ovarian cancer has a poor prognosis with a long-term survival in less than 30% of patients, whereas more than 90% of patients can be cured by conventional therapy when the disease is detected in stage I. No single marker is upregulated and shed in adequate amounts in early stages. Lu and colleagues screened the gene expression of 41,441 known genes and expressed sequence tags between five pools of normal ovarian surface epithelial cells and 42 epithelial ovarian cancers of different stages, grades, and histotypes to identify tumor markers (Clin Cancer Res 10:3291 (2004)). The study found four markers that were 3-fold upregulated and were able to distinguish all tumor samples from normal ovarian surface epithelial cells; one of these genes is Notch3. Other studies have also found that Notch3 expression is upregulated in a series of plasma cell neoplasm, including multiple myeloma, plasma cell leukemia, and extramedullary plasmacytoma (Hedvat, et al., Br J Haematol 122:728 (2003); pancreatic cancer (Buchler, et al., Ann Surg 242:791 (2005)); and T cell acute lymphoblastic leukemias (T-ALL) (Bellavia, et al., Proc Natl Acad Sci USA 99:3788 (2002); Screpanti, et al., Trends Mol Med 9:30 (2003)).
Also, CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) causes a type of stroke and dementia whose key features include recurrent subcortical ischaemic events and vascular dementia. CADASIL has been found to be associated with a mutant gene localized to chromosome 19 (Joutel, et al., Nature 383:707 (1996)). Joutel et al. identified mutations in CADASIL patients that cause serious disruption of the Notch 3 gene, indicating that Notch3 could be the defective protein in CADASIL patients. Unfortunately, this highly incapacitating and often lethal disease has remained largely undiagnosed or misdiagnosed as multiple sclerosis and Alzheimer's disease. Current studies would tend to demonstrate that it is a condition that is much more widespread than first thought. Efforts have been made to identify diagnostic tools for the disease and develop a therapy.
An additional example of a Notch 3 related disease is familial hemiplegic migraine (FHM), the dominant autosomal form of migraine with aura, located in the same region of chromosome 19 as the Notch3 gene. It should be noted that more than 30% of patients suffering from CADASIL also suffer from migraine with aura. However, the latter is observed in only about 5% of the population and this observation led to the discovery of Notch3 gene involvement in the mechanism of this condition. Similarly, familial paroxytic ataxia has been linked to a gene located in the same region of chromosome 19 and implicating Notch3 in this condition. Other conditions and diseases that have been linked to Notch3 include diabetes (Anastasi, et al., J Immunol 171:4504 (2003), rheumatoid arthritis (Yabe, et al., J Orthop Sci 10:589 (2005)), disease states in which vascular cell fate occur in vivo (Sweeney, et al., FASEB J 18:1421 (2004)), and Alagille syndrome (Flynn, et al., J Pathol 204:55 (2004)).
U.S. Pat. No. 5,786,158 describes diagnostic methods and compositions for the detection of malignancy or nervous system disorders based on the level of Notch proteins or nucleic acids. U.S. Application No. 20020151487 describes a diagnostic test to determine the expression levels of Notch ligands, receptors, or other Notch signaling compounds in cells.
Ongoing research studies are currently being pursued to identify other diseases and conditions linked to Notch3 expression. In view of the large number of human diseases associated with the Notch 3 signaling pathway, it is critical that new ways of detecting and diagnosing these diseases be identified. The current invention provides novel anti-Notch 3 antibodies useful for this unmet medical need.